The present invention relates to a charge tube assembly for a perforating gun.
Canadian Patent 2,243,178 (Buzinsky) discloses a charge tube retaining and orienting structure for a perforating gun. The Buzinsky reference describes use in the prior art of disk-form end plates which are held in place by screws. The Buzinsky reference then goes on to teach the use of externally threaded annular disks. These disks are positioned by threading into a threaded end of a carrier tube.
The present invention relates to an alternative charge tube assembly.
According to the present invention there is provided a charge tube assembly for a perforating gun which includes a tubular body having opposed ends. Integrally formed engagement members are positioned at each of the opposed ends. Detachable end plates are secured to each of the opposed ends. Each of the end plates has openings engagable with the engagement members.
The charge tube assembly, as described above, provides a number of advantages. It does not require screws or other fasteners. There is, therefore, no concern about handling or losing small components in the field. It can be made from thinner material as it does not need to have sufficient thickness to support the machining of an engagement thread. The result is an easy to handle and cost effective alternative to existing charge tube assemblies.
As will be further described with illustrated embodiments, once the basic teachings of the invention are understood the configuration of engagement member and configuration of detachable end plate can vary.
A preferred form of engagement which will hereinafter be illustrated and described for the first or upper one of the opposed ends has a peripheral edge with at least two circumferentially spaced inwardly extending axial slots along the peripheral edge forming arcuate engagement members. The engagement members having deformable locking tabs to prevent the accidental displacement of the end plate. One reason that this form of engagement is preferred relates to alignment. When the axial slots are asymmetrically positioned along the peripheral edge, the engagement members must be positioned in a particular orientation in order to engage the end plates. This addresses the alignment issue, as the detachable end plates can only fit in one orientation.
A preferred form of engagement for the second or lower engagement members is hook shaped. By rotation of the end plate when the engagement members are positioned in the openings of the end plate, the engagement members are moved into an engaged positioned engaging the end plate. For those end plates that are rotated into locking engagement, a tool coupling is positioned on the end plate which is adapted to engage a tool. One form of tool coupling will be illustrated, but alternative forms of tool coupling could be used.
An alternative and equally workable form of engagement involves the use of engagement members which are deformable. The engagement members are positioned in the openings of the end plates and then deformed to engage the end plates.
The configuration of the openings in the end plates can vary. An embodiment will hereinafter be illustrated and described in which the openings in the end plates are slots. An embodiments will also hereinafter be illustrated and described in which the openings in the end plates are cavities positioned along an inner sidewall which defines a central bore.